1. Field of the Invention
This invention relates to a novel and improved data module drive utilizing a sealed interchangeable data module.
2. Description of the Prior Art
Presently known magnetic disk file data storage facilities utilizing interchangeable disks or disk packs are configured in the form of a drive that includes read/write heads, head actuator means and a drive spindle. The disk pack may contain a single disk or several disks attached to a hub suitable for mounting on the drive spindle.
In this application, "interchangeable" shall refer to a medium, such as a disk module that has universal substitution without loss of data for use on all the devices with which it is developed to work. To be truly interchangeable, all of the hardware elements involved in the mechanical, electronic and magnetic implementation of storage must have sufficient repeatability, so that the summation of all the deviations from perfection, for all elements, does not exceed the total variance, i.e. engineering tolerance allowed.
The most common pack configuration presently in use is contained in a two part plastic cover assembly. The two part cover has a circular bottom panel section that is removed by the operator prior to installation of the pack on the drive spindle, and a cylindrical side section and top that is removed at the time the pack is mounted on the drive spindle. It is apparent that the removal of the pack covers exposes the pack to contamination during a loading/unloading cycle.
An alternate pack cover configuration provides for an integral cover assembly that remains with the pack. Data heads are inserted into the pack through a cover door that is opened during pack installation. The integral cover configuration provides some improved protection of the pack compared to the removal cover type. However, in both configurations, the drive data heads are exposed to contamination during the pack loading/unloading cycle.
A typical interchangeable disk pack file facility utilizes two or more data read/write heads mounted to a carriage assembly that positions the data heads over selected data track locations. These heads must be able to read any data track written on its associated disk surface in any similar file facility. Head position may be controlled by a mechanical detent acting on the head access means; or the heads may be positioned by a closed loop servo system using a servo reference and a servo position sensing transducer. Such control of radial head positioning relative to the data track is difficult and costly in a typical high track density, interchangeable pack file facility.
With the evolution of the magnetic disk file, increased bit and track densities and resultant increased storage capacity have been realized with increased actuator speed and access time. These improvements have required more accurate radial positioning of the data head relative to the disk surface. The close spacing of the head to the disk, which may now be in the order of 50 microinches or less, requires stringent control of the disk file apparatus to avoid head/disk damage, which may be caused by particle contamination, for example. However, the challenge remains to position uniformly all data heads controlled by the reference system to a radial position tolerance equivalent to a fraction of a track width. To permit pack interchangeability, all heads in all files must be similarly positioned.
Also, the achievement of increased bit density imposes requirements for more precise control of the skew alignment of the read/write heat gap. Misalignment of the read head gap relative to write head gap will cause reduced signal output and bit timing shifts that may cause read errors. Control of the skew alignment of all data heads to assure error free pack interchangeability may represent a significant portion of the manufacturing cost of each data head.
Furthermore, presently known disk storage files utilizing interchangeable disk packs must provide means for the retraction and loading of the data heads relative to the pack disk surfaces. The head retract-load function adds cost to the file and increases the exposure of the disk pack to damage resulting from head-disk impact during retract or load.
In addition, when inserting another disk pack into the file, the disks are usually at a different temperature than the head assemblies. This temperature differential, which is reflected in the radial dimensions of the disks relative to the lengths of the head arms, presents problems in the "Seek Track" function, and therefore a warmup period is needed prior to recording or readout. Consequently, there is an undue loss of costly computer operating time.